Combined heat flow and heat generation measurements in the Bohemian massif

Abstract

Six new heat flow values from western and north-western parts of the Bohemian massif are presented. Two of these heat flow measurements were combined with the determinations of heat generation due to the radioactive decay. The heat flow values fit the general geothermal pattern of Czechoslovakia ( Cermák 1968), of clearly sustained low heat flow in the stable parts of the Bohemian massif and increased heat flow in Krušné Hory mountains. The linear relationship between heat flow Q and heat generation A, Q = q o + b A , revealed preliminary values of b = 3.8 km and q o = 1.05 × 10 −6 cal/(cm 2s) , which may be of physical meaning for the uppermost crustal structure. However, such a low value of b does not seem to be adequate for deep extrapolation of surface heat flow observations and for the calculation of crustal temperature distribution. Characteristic deep temperatures of individual tectonic sub-units of the Bohemian massif were calculated using the «two-layers step modelå of the crust formed by granitic and basaltic layers. The Moho temperature and the upper mantle heat flow contribution are increasing from 500–550 to 650–700 °C and from 0.50–0.55 to 0.60–0.65 × 10 −6 cal/(cm 2s) respectively, beneath the most stable central part northward beneath the northern tectonically rejuvenated region of the Krušné Hory mountains.